U.S. patent application number 13/821653 was filed with the patent office on 2013-07-04 for gas decomposition component, power generation apparatus, and method for decomposing gas.
This patent application is currently assigned to SUMITOMO ELECTRIC INDUSTRIES, LTD.. The applicant listed for this patent is Tomoyuki Awazu, Hideyuki Doi, Chihiro Hiraiwa, Toshiyuki Kuramoto, Tetsuya Kuwabara, Masatoshi Majima, Naho Mizuhara, Toshio Ueda. Invention is credited to Tomoyuki Awazu, Hideyuki Doi, Chihiro Hiraiwa, Toshiyuki Kuramoto, Tetsuya Kuwabara, Masatoshi Majima, Naho Mizuhara, Toshio Ueda.
Application Number | 20130171542 13/821653 |
Document ID | / |
Family ID | 45993616 |
Filed Date | 2013-07-04 |
United States Patent
Application |
20130171542 |
Kind Code |
A1 |
Hiraiwa; Chihiro ; et
al. |
July 4, 2013 |
GAS DECOMPOSITION COMPONENT, POWER GENERATION APPARATUS, AND METHOD
FOR DECOMPOSING GAS
Abstract
A gas decomposition component includes a cylindrical membrane
electrode assembly (MEA) including a first electrode layer, a
cylindrical solid electrolyte layer, and a second electrode layer
in order from an inside toward an outside, in a layered structure,
wherein an end portion of the cylindrical MEA is sealed, a gas
guide pipe is inserted through another end portion of the
cylindrical MEA into an inner space of the cylindrical MEA to form
a cylindrical channel between the gas guide pipe and an inner
circumferential surface of the cylindrical MEA, and a gas flowing
through the gas guide pipe toward the sealed portion is made to
flow out of the gas guide pipe in a region near the sealed portion
so that a flow direction of the gas is reversed and the gas flows
through the cylindrical channel in a direction opposite to the flow
direction in the guide pipe.
Inventors: |
Hiraiwa; Chihiro;
(Osaka-shi, JP) ; Majima; Masatoshi; (Itami-shi,
JP) ; Kuwabara; Tetsuya; (Osaka-shi, JP) ;
Awazu; Tomoyuki; (Itami-shi, JP) ; Mizuhara;
Naho; (Itami-shi, JP) ; Ueda; Toshio;
(Itami-shi, JP) ; Doi; Hideyuki; (Itami-shi,
JP) ; Kuramoto; Toshiyuki; (Itami-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Hiraiwa; Chihiro
Majima; Masatoshi
Kuwabara; Tetsuya
Awazu; Tomoyuki
Mizuhara; Naho
Ueda; Toshio
Doi; Hideyuki
Kuramoto; Toshiyuki |
Osaka-shi
Itami-shi
Osaka-shi
Itami-shi
Itami-shi
Itami-shi
Itami-shi
Itami-shi |
|
JP
JP
JP
JP
JP
JP
JP
JP |
|
|
Assignee: |
SUMITOMO ELECTRIC INDUSTRIES,
LTD.
Osaka-shi, Osaka
JP
|
Family ID: |
45993616 |
Appl. No.: |
13/821653 |
Filed: |
October 13, 2011 |
PCT Filed: |
October 13, 2011 |
PCT NO: |
PCT/JP2011/073506 |
371 Date: |
March 8, 2013 |
Current U.S.
Class: |
429/497 |
Current CPC
Class: |
B01D 2258/0216 20130101;
H01M 4/8657 20130101; H01M 8/10 20130101; Y02E 60/50 20130101; B01D
2257/406 20130101; B01D 53/326 20130101; H01M 8/1007 20160201 |
Class at
Publication: |
429/497 |
International
Class: |
H01M 8/10 20060101
H01M008/10 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 28, 2010 |
JP |
2010-242207 |
Claims
1. A gas decomposition component comprising a cylindrical membrane
electrode assembly (MEA) including a cylindrical solid electrolyte
layer, a first electrode layer formed on an inner circumferential
portion of the solid electrolyte layer in a layered structure, and
a second electrode layer formed on an outer circumferential portion
of the solid electrolyte layer in a layered structure, wherein an
end portion of the cylindrical MEA is sealed, a gas guide pipe is
inserted through another end portion of the cylindrical MEA into an
inner space of the cylindrical MEA to form a cylindrical channel
between the gas guide pipe and an inner circumferential surface of
the cylindrical MEA, and a gas flowing through the gas guide pipe
toward the sealed portion is made to flow out of the gas guide pipe
in a region near the sealed portion so that a flow direction of the
gas is reversed and the gas flows through the cylindrical channel
in a direction opposite to the flow direction in the guide
pipe.
2. The gas decomposition component according to claim 1, wherein
the gas guide pipe is formed of a conductive material, and the gas
guide pipe is electrically connected to the first electrode layer
to constitute a collector for the first electrode layer.
3. The gas decomposition component according to claim 2, wherein a
conductive metal mesh sheet is disposed on an inner circumferential
surface of the first electrode layer, and the metal mesh sheet is
connected to the gas guide pipe to establish an electrical
connection between the first electrode layer and the gas guide
pipe.
4. The gas decomposition component according to claim 1, wherein a
porous conductive layer is disposed on a surface of the first
electrode layer.
5. The gas decomposition component according to claim 1, wherein
the end portion of the cylindrical MEA is sealed with a bottom
portion formed from an extension of the solid electrolyte
layer.
6. The gas decomposition component according to claim 1, wherein
the end portion of the cylindrical MEA is sealed with a sealing
member engaged with the end portion of the cylindrical MEA.
7. The gas decomposition component according to claim 1, wherein
the first electrode layer and/or the second electrode layer is a
fired body containing an ion-conductive ceramic and metal chain
particles mainly containing nickel (Ni).
8. The gas decomposition component according to claim 1, wherein
the solid electrolyte has oxygen-ion conductivity or proton
conductivity.
9. A power generation apparatus comprising the gas decomposition
component according to claim 1.
10. A method for decomposing a gas, the method being performed with
a gas decomposition component including a cylindrical membrane
electrode assembly (MEA) including a cylindrical solid electrolyte
layer, a first electrode layer formed on an inner circumferential
portion of the solid electrolyte layer in a layered structure, and
a second electrode layer formed on an outer circumferential portion
of the solid electrolyte layer in a layered structure, comprising:
sealing an end portion of the cylindrical MEA to form a sealed
portion; arranging a gas guide pipe so that the gas guide pipe is
inserted through another end portion of the cylindrical MEA into an
inner space of the cylindrical MEA; allowing the gas to flow
through the gas guide pipe toward the sealed portion, and to flow
out of the gas guide pipe in a region near the sealed portion so
that a flow direction of the gas is reversed; and allowing the gas
to flow through a cylindrical channel formed between the gas guide
pipe and an inner circumferential surface of the cylindrical MEA,
in a direction opposite to the flow direction in the guide pipe so
that the gas is decomposed.
Description
TECHNICAL FIELD
[0001] The present invention relates to a gas decomposition
component, a power generation apparatus, and a method for
decomposing a gas. Specifically, the present invention relates to a
gas decomposition component that can efficiently decompose a
predetermined gas, a power generation apparatus including the gas
decomposition component, and a method for decomposing a gas.
BACKGROUND ART
[0002] For example, although ammonia is an essential compound in
agriculture and industry, it is hazardous to humans and hence there
are various known methods for decomposing ammonia in water and the
air. A method for removing ammonia through decomposition from water
containing ammonia at a high concentration has been proposed:
aqueous ammonia being sprayed is brought into contact with airflow
to separate ammonia into the air and the ammonia is brought into
contact with a hypobromous acid solution or sulfuric acid (Patent
Literature 1). Other methods have also been proposed: ammonia is
separated into the air by the same process as in the
above-described method and the ammonia is incinerated with a
catalyst (Patent Literature 2); and ammonia-containing wastewater
is decomposed with a catalyst into nitrogen and water (Patent
Literature 3). In general, waste gas from semiconductor fabrication
equipment contains ammonia, hydrogen, and the like. To completely
remove the odor of ammonia, the amount of ammonia needs to be
reduced to the ppm order. For this purpose, a method has been
commonly used in which waste gas to be released from semiconductor
equipment is passed through scrubbers so that water containing
chemicals absorbs the hazardous gas. On the other hand, in order to
decompose a hazardous gas at a low running cost without supply of
energy, chemicals, or the like, a treatment method for waste gas
from semiconductor fabrication equipment or the like has also been
proposed: ammonia is decomposed with a phosphoric acid fuel cell
(Patent Literature 4).
CITATION LIST
Patent Literature
[0003] PTL 1: Japanese Unexamined Patent Application Publication
No. 7-31966 [0004] PTL 2: Japanese Unexamined Patent Application
Publication No. 7-116650 [0005] PTL 3: Japanese Unexamined Patent
Application Publication No. 11-347535 [0006] PTL 4: Japanese
Unexamined Patent Application Publication No. 2003-45472 [0007] PTL
5: Japanese Patent No. 3238086
SUMMARY OF INVENTION
Technical Problem
[0008] Ammonia can be decomposed by the method of using a chemical
solution such as a neutralizing agent as described in PTL 1, the
incineration method as described in PTL 2, or the method employing
a thermal decomposition reaction with a catalyst as described in
PTL 3. However, these methods have problems that they require
chemicals and external energy (fuel) and also require periodic
replacement of the catalyst, resulting in high running costs.
[0009] In addition, such an apparatus has a large size and it is
difficult to provide a space for additional installation of the
apparatus in existing equipment. The apparatus in which a
phosphoric acid fuel cell is used to remove ammonia in waste gas
from compound semiconductor fabrication also has a problem: since
the electrolyte is liquid, the size of air-side and ammonia-side
separators cannot be reduced and it is difficult to reduce the size
of the apparatus.
[0010] In order to address the above-described problems, as
described in PTL 5, a cylindrical membrane electrode assembly (MEA)
may be employed that includes a cylindrical solid electrolyte
layer, and a first electrode layer and a second electrode layer
that are formed on the inner and outer surfaces of the solid
electrolyte layer so as to sandwich the solid electrolyte layer in
a layered structure. A gaseous fluid containing a gas to be
decomposed is made to flow through the inner space of the
cylindrical MEA in the axial direction.
[0011] In order to decompose the gas, the temperature of the
gaseous fluid containing the gas is preferably increased as high as
possible and the gas is supplied to the first electrode layer (fuel
electrode) of the cylindrical MEA. For this reason, a heater that
heats the entirety of the cylindrical MEA is provided. In order to
decompose a large amount of a gas, the flow rate of the gas flowing
through the cylindrical MEA needs to be increased. However, when
the gas flow rate is increased, the gas that is not sufficiently
heated is supplied to the cylindrical MEA and the gas decomposition
efficiency is decreased, which is problematic.
[0012] In an existing cylindrical MEA, connection members are
connected to both end portions of the cylindrical MEA so that a gas
is made to flow through the inner space of the cylindrical MEA in
one direction. However, as described above, since the entirety of
the cylindrical MEA is kept at a high temperature, the effect of
sealing between both end portions of the cylindrical MEA and the
connection members tends to degrade and the connection reliability
is low, which is problematic.
[0013] An object of the present invention is to provide a gas
decomposition component in which an electrochemical reaction using
a solid electrolyte is employed to reduce the running cost and to
provide high treatment performance, and the temperature of a gas
flowing through a cylindrical MEA is increased to enhance the
decomposition efficiency.
Solution to Problem
[0014] A gas decomposition component according to an embodiment of
the present invention includes a cylindrical membrane electrode
assembly (MEA) including a cylindrical solid electrolyte layer, a
first electrode layer formed on an inner circumferential portion of
the solid electrolyte layer in a layered structure, and a second
electrode layer formed on an outer circumferential portion of the
solid electrolyte layer in a layered structure, wherein an end
portion of the cylindrical MEA is sealed, a gas guide pipe is
inserted through another end portion of the cylindrical MEA into an
inner space of the cylindrical MEA to form a cylindrical channel
between the gas guide pipe and an inner circumferential surface of
the cylindrical MEA, and a gas flowing through the gas guide pipe
toward the sealed portion is made to flow out of the gas guide pipe
in a region near the sealed portion so that a flow direction of the
gas is reversed and the gas flows through the cylindrical channel
in a direction opposite to the flow direction in the guide
pipe.
[0015] Specifically, in a gas decomposition component according to
the present invention, a gas to be decomposed is made to flow into
a gas guide pipe and back again in the axial direction.
[0016] When the above-described configuration is employed, the gas
is made to flow for a distance equal to twice the cylinder length
of the cylindrical MEA. Accordingly, after the temperature of the
gas is increased by sufficient heating within the guide pipe, the
gas can be supplied to the cylindrical MEA. As a result, the gas
decomposition efficiency can be enhanced and the gas flow rate can
be increased to increase the gas treatment rate.
[0017] An inlet and an outlet for the gas in a cylindrical MEA can
be both located in a single end portion of the cylindrical MEA. As
a result, the reliability of a sealing structure between the
cylindrical MEA and a connection pipe or the like can be
enhanced.
[0018] The configuration in which an end portion of the cylindrical
MEA is sealed is not particularly limited. For example, according
to another embodiment of the present invention, the end portion of
the cylindrical MEA may be sealed with a bottom portion formed from
an extension of the solid electrolyte layer. The bottom portion is
formed as an integral part of the cylindrical MEA in forming and
sintering steps. Accordingly, gas leakage does not occur and the
end portion of the cylindrical MEA can be sealed with
certainty.
[0019] Alternatively, according to another embodiment of the
present invention, the end portion of the cylindrical MEA may be
sealed with a sealing member engaged with the end portion of the
cylindrical MEA. By employing such a configuration, the present
invention can be applied to an existing cylindrical MEA having two
open ends.
[0020] A gas inlet and a gas outlet in a cylindrical MEA according
to the present invention can be constituted by a pipe member having
a double structure for the purpose of not causing mixing of a gas
to be decomposed and decomposed gases. For example, a
heat-resistant pipe joint through which gases are introduced and
discharged can be provided in an open end portion of the
cylindrical MEA. The pipe joint includes a gas introduction part
that is in communication with the gas guide pipe and an annular
exhaust space that surrounds an outer circumferential portion of
the gas guide pipe and that has a gas discharge part in a side
portion of the exhaust space. By employing the pipe joint, a
gaseous fluid containing a gas to be decomposed can be introduced
into an end of the cylindrical MEA and a gaseous fluid containing
decomposed gases can also be discharged from the end of the
cylindrical MEA.
[0021] According to another embodiment of the present invention,
the gas guide pipe is formed of a conductive material, and the gas
guide pipe is electrically connected to the first electrode layer
to constitute a collector for the first electrode layer.
[0022] By using the gas guide pipe as a collector for the first
electrode layer, the gas decomposition efficiency can be enhanced
and the space within the cylindrical MEA can also be effectively
used.
[0023] A material for forming the gas guide pipe is not
particularly limited unless corrosion or the like is caused by a
gas to be decomposed. The gas guide pipe may be formed of, for
example, stainless steel, copper, nickel, or a nickel alloy such as
inconel (registered trademark of Special Metals Corporation).
[0024] A technique of establishing an electrical connection between
the first electrode layer and the gas guide pipe is not
particularly limited. For example, a porous metal body may be
inserted into a cylindrical channel formed between the inner
circumferential surface of the cylindrical MEA and the outer
circumferential surface of the gas guide pipe to thereby establish
an electrical connection between the first electrode layer and the
gas guide pipe. By disposing the porous metal body, the cylindrical
channel between the inner circumferential surface of the first
electrode layer and the outer circumferential surface of the gas
guide pipe can be ensured and the gas guide pipe can also be held
at a position in the cylindrical MEA. However, for example, when
the cylindrical MEA has a small diameter, it is difficult to
achieve a large contact area or a high contact pressure between the
porous metal body and the first electrode layer and the gas guide
pipe; thus, the resistance between these members may be high.
[0025] Regarding a technique for avoiding such a disadvantage,
according to another embodiment of the present invention, a
conductive metal mesh sheet may be disposed on an inner
circumferential surface of the first electrode layer, and the metal
mesh sheet may be connected to the gas guide pipe to establish an
electrical connection between the first electrode layer and the gas
guide pipe.
[0026] By holding the metal mesh sheet so as to be in contact with
the first electrode layer, the resistance between the electrode
layer and the metal mesh sheet can be decreased. In addition, by
directly connecting the metal mesh sheet to the gas guide pipe, the
contact resistance between the collectors can be further decreased.
For example, the following configuration may be employed: a single
metal mesh sheet is disposed so as to be in contact with the
entirety of the inner circumferential surface of the first
electrode layer, and an end portion of the metal mesh sheet is
converged around the outer circumferential surface of the gas guide
pipe.
[0027] When the above-described configuration is employed, the
collector can be made to have a large area by using the gas guide
pipe. Thus, the gas decomposition efficiency can be further
enhanced.
[0028] The porous metal body may be inserted between the metal mesh
sheet and the gas guide pipe to back up the metal mesh sheet from
inside. As a result, the contact resistance between the first
electrode layer and the collector can be decreased. In such a
configuration, the following two conduction paths are formed: (1)
Ni mesh sheet 11a/porous metal body 11s/gas guide pipe 11k and (2)
Ni mesh sheet 11a/gas guide pipe 11k. As a result, while the
contact resistance of the anode collector can be further decreased,
an increase in pressure loss can be suppressed.
[0029] The form of the metal mesh sheet is not particularly
limited. For example, the metal mesh sheet may be formed in the
shape of a cylinder and disposed so as to cover the entire surface
of the first electrode layer.
[0030] The appearance configuration of the metal mesh sheet is also
not particularly limited. For example, a woven fabric, a nonwoven
fabric, a perforated sheet or the like may be employed. In order to
ensure flexibility, uniformity of pore size, or the like, a woven
fabric is preferably employed.
[0031] A metal material for forming the metal mesh sheet is also
not particularly limited. For example, a metal mesh sheet formed of
a material such as Ni, Ni--Fe, Ni--Co, Ni--Cr, or Ni--W is
preferably employed. A metal mesh sheet having a surface layer such
as a silver-plated layer may be employed. When the occurrence of a
catalytic reaction is intended, a metal mesh sheet formed of a
material such as Ni--W is preferably employed.
[0032] According to another embodiment of the present invention, a
porous conductive layer is preferably disposed on a surface of the
first electrode layer. There may be cases where it is difficult to
achieve uniform contact between the metal mesh sheet and the
entirety of the inner circumferential surface of the first
electrode layer. Specifically, the contact pressure between the
surface of the first electrode layer and the metal mesh sheet may
be varied or the metal mesh sheet may be partially separated from
the surface of the first electrode layer.
[0033] By forming the conductive layer on the surface of the first
electrode layer, conductivity between the first electrode layer and
the mesh sheet can be ensured in the entire region. Since the
conductive layer is porous, the gas is not prevented from coming
into contact with the first electrode layer.
[0034] The porous conductive layer disposed may be a porous
conductive-paste-coated layer. By disposing a porous
conductive-paste-coated layer on the inner circumferential surface
of the first electrode layer, an electrical connection between the
first electrode layer and the metal mesh sheet is established with
certainty with the conductive-paste-coated layer therebetween; and
the electric resistance between the first electrode layer and the
gas guide pipe can also be decreased.
[0035] Specifically, by disposing the conductive-paste-coated
layer, a surface of the metal mesh sheet is partially embedded in
the conductive-paste-coated layer so that the electrical connection
between the metal mesh sheet and the first electrode layer can be
established with certainty; thus, the contact resistance
therebetween can be considerably decreased. In addition, the entire
surface of the metal mesh sheet can be uniformly made to be in
contact with the first electrode layer. Accordingly, a local
increase in the electric resistance between the first electrode
layer and the metal mesh sheet does not occur. By forming the
conductive-paste-coated layer by application over the entire
surface of the first electrode layer, even when the metal mesh
sheet is separated from the conductive-paste-coated layer, current
collection on the surface of the first electrode layer can be
ensured. Thus, even when a portion of the metal mesh sheet is
separated from the conductive-paste-coated layer due to the
influence of, for example, temperature, the current-collecting
effect is not degraded. In addition, since the
conductive-paste-coated layer is porous, the gas is not prevented
from coming into contact with the first electrode layer.
Accordingly, the electrochemical reaction can be uniformly caused
in the entire region of the first electrode layer to considerably
enhance the gas decomposition reaction efficiency. Thus, the gas
decomposition treatment performance can be enhanced.
[0036] The porous conductive-paste-coated layer can be formed from
pastes containing various conductive particles. For example, the
porous conductive-paste-coated layer can be formed from a paste
containing silver particles. Silver particles have high
conductivity and can cause a decrease in the electric resistance of
the collector for the first electrode layer to enhance the gas
decomposition treatment performance. Silver particles also have
high stability and are not substantially oxidized.
[0037] Materials for forming the first electrode layer and the
second electrode layer are also not particularly limited.
[0038] For example, according to another embodiment of the present
invention, the first electrode layer and/or the second electrode
layer may be a fired body containing an ion-conductive ceramic and
metal chain particles mainly containing nickel (Ni). The metal
chain particles denote an elongated moniliform metal substance in
which metal particles are connected together. The metal is
preferably Ni, Fe-containing Ni, Ni containing a trace amount of
Ti, or Fe-containing Ni containing a trace amount of Ti. When the
surface of Ni or the like is oxidized, the surfaces of the metal
chain particles are oxidized while the contents (portions inside
the surface layers) are not oxidized and have metal
conductivity.
[0039] Accordingly, for example, when ions moving through the solid
electrolyte layer are anions (the ions may be cations), the
following effects are provided.
[0040] (A1) When the first electrode layer (anode) is formed so as
to contain metal chain particles, in the first electrode layer
(anode), the chemical reaction between the anions moving through
the solid electrolyte layer and gas molecules in a gaseous fluid
introduced into the first electrode layer (anode) from the outside
thereof is promoted (catalysis) with the oxide layers of the metal
chain particles and the chemical reaction in the first electrode
layer (anode) is also promoted (promotion effect due to charges)
through participation of the anions. The conductivity of electrons
generated by the chemical reaction can be ensured in the metal
portions of the metal chain particles. As a result, the
electrochemical reaction accompanying giving and receiving of
charges in the first electrode layer (anode) can be promoted on the
whole. When the first electrode layer (anode) contains metal chain
particles, in the first electrode layer (anode), cations such as
protons are generated and the cations move through the solid
electrolyte layer to the second electrode layer (cathode) to
thereby similarly provide the above-described promotion effect due
to charges.
[0041] Note that, prior to use, the oxide layers of the metal chain
particles are formed by firing with certainty; however, during use,
the oxide layers are often eliminated by the reduction reaction.
Even when the oxide layers are eliminated, the above-described
catalysis is not eliminated though it may reduce. In particular, Ni
that contains Fe or Ti has high catalysis in spite of the absence
of the oxide layers.
[0042] (A2) When the second electrode layer (cathode) is formed so
as to contain the metal chain particles, in the second electrode
layer (cathode), the chemical reaction of gas molecules in a
gaseous fluid introduced into the second electrode layer (cathode)
from the outside thereof is promoted (catalysis) with the oxide
layers of the metal chain particles; and electron conductivity from
the external circuit is enhanced and, through participation of the
electrons, the chemical reaction in the second electrode layer
(cathode) is also promoted (promotion effect due to charges). Thus,
anions are efficiently generated from the molecules and can be sent
to the solid electrolyte layer. As with (A1), in (A2), the
electrochemical reaction among cations having moved through the
solid electrolyte layer, electrons having flowed through the
external circuit, and the second gaseous fluid can be promoted.
Accordingly, as in the case where the first electrode layer (anode)
contains the metal chain particles, the electrochemical reaction
accompanying giving and receiving of charges in the second
electrode layer (cathode) can be promoted on the whole. Whether the
second electrode layer (cathode) is formed so as to contain the
metal chain particles or not depends on the gas to be
decomposed.
[0043] (A3) When the first electrode layer (anode) and the second
electrode layer (cathode) are formed so as to contain the metal
chain particles, the above-described effects in (A1) and (A2) can
be obtained.
[0044] The rates of the above-described electrochemical reactions
are often limited by the speed at which ions move through the solid
electrolyte layer or the time for which ions move through the solid
electrolyte layer. To increase the movement speed of ions, the gas
decomposition component is generally equipped with a heating unit
such as a heater and heated at a high temperature such as
600.degree. C. to 1000.degree. C.
[0045] By the heating to a high temperature, in addition to an
increase in the movement speed of ions, chemical reactions
accompanying giving and receiving of charges in the electrode
layers can be promoted.
[0046] When the ions moving through the solid electrolyte layer are
anions, as described above, the anions are generated by the
chemical reaction in the second electrode layer (cathode) and
supplied. The anions are generated in the second electrode layer
(cathode) through the reaction between molecules of a fluid
introduced and electrons. The generated anions move through the
solid electrolyte layer to the first electrode layer (anode). The
electrons participating in the reaction of the second electrode
layer (cathode) move from the external circuit (including a
capacitor, a power supply, and a power consumption device)
connecting the first electrode layer (anode) and the second
electrode layer (cathode). When the ions moving thorough the solid
electrolyte layer are cations, the cations are generated by the
electrochemical reaction in the first electrode layer (anode) and
move through the solid electrolyte layer to the second electrode
layer (cathode). Electrons are generated in the first electrode
layer (anode) and flow through the external circuit to the second
electrode layer (cathode) and participate in the electrochemical
reaction in the second electrode layer (cathode). The
electrochemical reactions may be power generation reactions of a
fuel cell or may be electrolytic reactions.
[0047] According to another embodiment of the present invention,
the solid electrolyte may have oxygen-ion conductivity or proton
conductivity. When an oxygen-ion-conductive solid electrolyte is
used, for example, a reaction between electrons and oxygen
molecules is caused to generate oxygen ions in the second electrode
layer (cathode), the oxygen ions move through the solid electrolyte
layer, and the predetermined electrochemical reaction can be caused
in the first electrode layer (anode). In this case, since the speed
at which the oxygen ions move through the solid electrolyte layer
is not higher than that of protons, to achieve a decomposition
capacity on the practical level, for example, the following
expedients are required: a sufficiently high temperature is
provided and/or the thickness of the solid electrolyte layer is
made sufficiently small.
[0048] On the other hand, as proton-conductive solid electrolytes,
barium zirconate (BaZrO.sub.3) and the like are known. When a
proton-conductive solid electrolyte is used, for example, ammonia
is decomposed in the first electrode layer (anode) to generate
protons, nitrogen molecules, and electrons; the protons move
through the solid electrolyte layer to the second electrode layer
(cathode) and react with oxygen in the second electrode layer
(cathode) to generate water (H.sub.2O). Protons are smaller than
oxygen ions and hence move through the solid electrolyte layer at a
higher speed than oxygen ions. Accordingly, at a lower heating
temperature, a decomposition capacity on the practical level can be
achieved.
[0049] For example, when ammonia is decomposed with a cylindrical
MEA in which an oxygen-ion-conductive solid electrolyte is used, a
reaction of generating water is caused in the first electrode layer
(anode) of the cylindrical MEA. The water takes the form of water
droplets at low-temperature portions near the outlet and may cause
pressure loss. In contrast, when a proton-conductive solid
electrolyte is used, protons, oxygen molecules, and electrons are
generated in the second electrode layer (cathode) (outside). Since
the outside is substantially open, even when adhesion of water
droplets occurs, pressure loss is less likely to be caused.
[0050] According to another embodiment of the present invention, a
power generation apparatus can be provided in which a gas to be
decomposed is used as fuel and a gas decomposition component is
used to constitute a fuel cell.
[0051] The gas to be decomposed is also not particularly limited.
For example, any one of the above-described gas decomposition
components is disposed; and a gaseous fluid containing ammonia may
be introduced into the first electrode layer and a gaseous fluid
containing oxygen molecules may be introduced into the second
electrode layer. In this case, oxygen ions generated in the second
electrode layer (cathode) move to the first electrode layer
(anode); the reaction between ammonia and oxygen ions is caused in
the first electrode layer under the catalysis due to metal chain
particles and the promotion effect due to ions; and electrons
generated by the reaction can be rapidly moved.
[0052] A gas decomposition component according to the present
invention will be used not only in gas detoxification but also as
bases of apparatuses in the fields of fuel cells and original
electrochemical reaction apparatuses using gas decomposition, to
thereby contribute to, for example, enhancement of the efficiency
of electrochemical reactions, size reduction of apparatuses, and
low running costs.
Advantageous Effects of Invention
[0053] A gas decomposition apparatus that has high gas
decomposition efficiency, operates at a low running cost, and has
high gas decomposition efficiency can be provided.
BRIEF DESCRIPTION OF DRAWINGS
[0054] FIG. 1 is a longitudinal sectional view of, on an end side
(sealed side), a gas decomposition component according to a first
embodiment of the present invention.
[0055] FIG. 2 is a sectional view taken along line IB-IB in FIG.
1.
[0056] FIG. 3 illustrates the electric wiring system of the gas
decomposition component in FIG. 1.
[0057] FIG. 4 is a longitudinal sectional view of, on a gas
inlet-outlet side, the gas decomposition component in FIG. 1.
[0058] FIG. 5 is a longitudinal sectional view illustrating a
second embodiment of the present invention.
DESCRIPTION OF EMBODIMENTS
[0059] Hereinafter, embodiments of the present invention will be
specifically described with reference to the drawings.
[0060] FIG. 1 is a longitudinal sectional view of a gas
decomposition component 10 according to a first embodiment of the
present invention. FIG. 2 is a sectional view taken along line
IB-IB in FIG. 1. In the present embodiments, in particular, cases
where the present invention is applied to a gas decomposition
component for decomposing ammonia gas are described.
[0061] In the gas decomposition component 10, a first electrode
layer (anode) 2 is disposed so as to cover the inner surface of a
cylindrical solid electrolyte layer 1, and a second electrode layer
(cathode) 5 is disposed so as to cover the outer surface of the
solid electrolyte layer 1; thus, a cylindrical MEA 7 (1, 2, 5) is
provided. The first electrode layer (anode) 2 may be referred to as
a fuel electrode. The second electrode layer (cathode) 5 may be
referred to as an air electrode. As illustrated in FIG. 1, the
cylindrical MEA 7 (1, 2, 5) according to the present embodiment has
a right-cylindrical shape. Although the cylindrical MEA 7 has an
inner diameter of, for example, about 20 mm, the dimensions and the
like thereof may be defined in accordance with apparatuses to which
the cylindrical MEA 7 is applied.
[0062] In the gas decomposition component 10 according to the
present embodiment, an end portion of the cylindrical MEA is sealed
and a gas guide pipe 11k formed of stainless steel is inserted
through another end portion of the cylindrical MEA. In the present
embodiment, since the gas guide pipe Ilk functions as a collector,
the gas guide pipe 11k is preferably formed of a material having a
low electric resistance. A suitable material may be selected in
accordance with the type of the gas. For example, the gas guide
pipe 11k may be formed of, other than the above-described stainless
steel, copper, nickel, or a nickel alloy such as inconel
(registered trademark of Special Metals Corporation). At the
above-described end portion, extensions of the solid electrolyte
layer 1 and the inner electrode layer 2 of the cylindrical MEA 7
are used to form a bottom portion; thus, a sealed portion 44 is
provided.
[0063] The gas guide pipe 11k is inserted through the other end
portion toward the above-described end portion of the cylindrical
MEA to form a cylindrical channel 43 between the inner
circumferential surface of the first electrode layer 2 of the
cylindrical MEA and the outer circumferential surface of the gas
guide pipe 11k. In this cylindrical channel, a porous metal body is
inserted to hold the gas guide pipe 11k in the central portion of
the cylindrical channel; thus the cylindrical channel 43 is formed
between the outer circumferential surface of the gas guide pipe Ilk
and the inner surface of the first electrode layer 2.
[0064] In a gas decomposition component according to the present
invention, a gas flowing through the gas guide pipe 11k toward the
sealed portion 44 is made to flow out of the gas guide pipe 11k in
a region near the sealed portion 44 so that the flow direction of
the gas is reversed and the gas flows through the cylindrical
channel 43 in a direction opposite to the flow direction in the
guide pipe 11k.
[0065] When such a configuration is employed, the gas is made to
flow within the cylindrical MEA 7 for a distance equal to about
twice the cylinder length of the cylindrical MEA. Accordingly,
after the temperature of the gas is increased by sufficient heating
within the gas guide pipe 11k, the gas can be supplied to the
cylindrical MEA 7. As a result, the gas decomposition efficiency
can be enhanced and the gas flow rate can be increased to increase
the gas treatment rate.
[0066] The gas guide pipe 11k is formed of a conductive metal such
as stainless steel and functions as a member of an anode collector
11. On the other hand, a cathode collector 12 is disposed so as to
wind around the outer surface of the second electrode layer
(cathode) 5.
[0067] The anode collector 11 includes a silver-paste-coated layer
11g, a Ni mesh sheet 11a, a porous metal body 11s, and the gas
guide pipe 11k. The Ni mesh sheet 11a is in contact with the first
electrode layer 2 (anode) on the inner-surface side of the
cylindrical MEA 7, with the silver-paste-coated layer 11g
therebetween, so that electric conduction from the porous metal
body 11s to the gas guide pipe 11k is achieved. In a region near
the sealed portion 44, an end portion W.sub.1 of the Ni mesh sheet
11a is electrically connected to the gas guide pipe Ilk so as to be
wound around the outer circumferential portion of the gas guide
pipe Ilk with a band-shaped connection member W.sub.2. Accordingly,
the Ni mesh sheet 11a forms, in parallel, (1) an electric
conduction path of Ni mesh sheet 11a/porous metal body 11s/gas
guide pipe 11k and (2) an electric conduction path of Ni mesh sheet
11a/gas guide pipe 11k. As a result, the anode collector 11 can be
provided on the inner surface of the cylindrical MEA 7 such that a
low electric resistance can be maintained and an increase in the
pressure loss can also be suppressed.
[0068] The porous metal body 11s is preferably a metal-plated body
that can be formed so as to have a high porosity such as Celmet
(registered trademark: Sumitomo Electric Industries, Ltd.) for the
purpose of decreasing the pressure loss of a gas such as ammonia
gas. In order to decrease the electric resistance between the first
electrode layer (anode) 2 and the anode collector 11, the
silver-paste-coated layer 11g and the Ni mesh sheet 11a are
disposed.
[0069] The cathode collector 12 includes a silver-paste-coated
wiring 12g and a Ni mesh sheet 12a. In the present embodiment, the
Ni mesh sheet 12a is in contact with the outer surface of the
cylindrical MEA 7 to conduct electricity to the external wiring.
The silver-paste-coated wiring 12g contains silver serving as a
catalyst for promoting decomposition of oxygen gas into oxygen ions
in the second electrode layer (cathode) 5 and also contributes to a
decrease in the electric resistance of the cathode collector 12.
The silver-paste-coated wiring 12g having predetermined properties
allows passing of oxygen molecules therethrough and contact of
silver particles with the second electrode layer (cathode) 5. Thus,
catalysis similar to that would be provided by silver particles
contained in the second electrode layer (cathode) 5 is exhibited.
In addition, this is less expensive than the case where the second
electrode layer (cathode) is formed so as to contain silver
particles.
[0070] FIG. 3 illustrates the electric wiring system of the gas
decomposition component 10 in FIG. 1 when the solid electrolyte
layer 1 is oxygen-ion conductive. An ammonia-containing gaseous
fluid is introduced through the gas guide pipe 11k into the
innermost portion of the inner cylinder of the cylindrical MEA 7,
which is highly airtight; that is, the gaseous fluid is guided to a
region near the sealed portion 44. Since the entirety of the
cylindrical MEA 7 is heated by a heater 41 to about 800.degree. C.,
the temperature of the gaseous fluid is increased while the gaseous
fluid flows through the gas guide pipe 11k. At this time, a portion
of the ammonia gas is decomposed by heating in the gas guide pipe
11k:
2NH.sub.3.fwdarw.N.sub.2+3H.sub.2.
[0071] For the purpose of holding the gas guide pipe Ilk at a
position inside the cylindrical MEA 7 to ensure the cylindrical
channel 43 and for the purpose of making a gaseous fluid containing
a gas to be decomposed flow, the porous metal body 11s is used. In
view of achieving a low pressure loss in the cylindrical channel,
as described above, the porous metal body 11s disposed in the
cylindrical channel 43 may be a porous metal-plated body such as
Celmet described above. In the cylindrical channel 43, while the
ammonia-containing gaseous fluid passes through pores in the porous
metal body 11s, the Ni mesh sheet 11a, and the porous
silver-paste-coated layer 11g, it comes into contact with the first
electrode layer (anode) 2, resulting in an ammonia decomposition
reaction described below.
[0072] Oxygen ions O.sup.2- are generated by an oxygen gas
decomposition reaction in the second electrode layer (cathode) 5
and pass through the solid electrolyte layer 1 to reach the first
electrode layer (anode) 2. That is, this is an electrochemical
reaction in the case where oxygen ions, which are anions, move
through the solid electrolyte layer 1.
[0073] In the first electrode layer (anode), the following reaction
occurs.
2NH.sub.3+3O.sup.2-.fwdarw.N.sub.2+3H.sub.2O+6e.sup.- (Anode
reaction)
[0074] Specifically, a portion of ammonia reacts:
2NH.sub.3.fwdarw.N.sub.2+3H.sub.2. These 3H.sub.2 react with the
oxygen ions 3O.sup.2- to generate 3H.sub.2O. The air, in
particular, oxygen gas is passed through a space S and introduced
into the second electrode layer (cathode) 5. Oxygen ions
dissociated from oxygen molecules in the second electrode layer
(cathode) 5 are sent to the solid electrolyte layer 1 toward the
first electrode layer (anode) 2.
[0075] In the first electrode layer (cathode) 5, the following
reaction occurs.
O.sub.2+4e.sup.-.fwdarw.2O.sup.2- (Cathode reaction)
[0076] As a result of the electrochemical reaction, electric power
is generated; a potential difference is generated between the first
electrode layer (anode) and the second electrode layer (cathode) 5;
current I flows from the cathode collector 12 to the anode
collector 11. When a load, such as the heater 41 for heating the
gas decomposition component 10, is connected between the cathode
collector 12 and the anode collector 11, electric power for the
heater 41 can be supplied. This supply of electric power to the
heater 41 may be a partial supply.
[0077] In most cases, the amount of supply from the self power
generation is equal to or lower than half of the overall electric
power required for the heater.
[0078] In the gas decomposition component 10, it is important that,
in the first electrode layer (anode) 2 disposed on the
inner-surface side of the cylindrical MEA 7, while the electric
resistance of the anode collector 11 is made low, the pressure loss
in the gaseous fluid passing through the anode collector 11 is made
low. On the second electrode layer (cathode) 5 side, it is
important that, although the air does not pass through the
cylinder, the density of contact points between the air and the
second electrode layer (cathode) 5 is made high and the resistance
of the cathode collector 12 is also made low.
[0079] The above-described electrochemical reaction is one in which
oxygen ions, which are anions, move through the solid electrolyte
layer 1. In another desirable embodiment according to the present
invention, for example, the solid electrolyte layer 1 is composed
of barium zirconate (BaZrO.sub.3) and a reaction is caused in which
protons are generated in the first electrode layer (anode) 2 and
moved through the solid electrolyte layer 1 to the second electrode
layer (cathode) 5.
[0080] When a proton-conductive solid electrolyte layer is used,
for example, in the case of decomposing ammonia, ammonia is
decomposed in the first electrode layer (anode) 2 to generate
protons, nitrogen molecules, and electrons; the protons are moved
through the solid electrolyte layer to the second electrode layer
(cathode) 5; and, in the second electrode layer (cathode), the
protons react with oxygen to generate water (H.sub.2O). Since
protons are smaller than oxygen ions, they move through the solid
electrolyte layer at a higher speed than oxygen ions. Accordingly,
while the heating temperature can be decreased, the decomposition
capacity on the practical level can be achieved. In addition, the
solid electrolyte layer can be formed so as to have a thickness
providing a sufficiently high strength.
[0081] FIG. 4 illustrates a connection state between the gas guide
pipe 11k and an external wire 11e and a connection state between
the cylindrical MEA 7, a gas transfer passage 45, and a gas exhaust
passage 55. A pipe joint 30 formed of a fluorocarbon resin is
engaged with the open end portion of the cylindrical MEA 7.
[0082] The pipe joint 30 is connected such that an O-ring 33
contained on the inner-surface side of an engagement portion 31b
extending from a body portion 31 to the solid electrolyte layer 1
butts against the outer surface of the solid electrolyte layer 1
composed of a ceramic, which is a fired body. The engagement
portion 31b of the pipe joint 30 is formed so as to have a tapering
outer diameter. This tapered portion is threaded and, to this
thread, a circular nut 32 is screwed. By screwing the circular nut
in the direction in which the outer diameter increases, the
engagement portion 31b is tightened in its outer surface. Thus, the
airtightness provided with the O-ring 33 can be adjusted.
[0083] On a side opposite to the engagement portion 31b of the pipe
joint 30, a gas introduction part 31a for introducing a gaseous
fluid containing the gas into the gas guide pipe 11k and a gas
discharge part 31c for discharging gases generated by decomposition
in the cylindrical MEA 7 are provided.
[0084] The pipe joint 30 includes therein a gas introduction
passage 45e having an engagement portion 45d that can be engaged
with a base end portion 11d of the gas guide pipe 11k in an
airtight manner. A gaseous fluid containing a gas to be decomposed
is made to flow through the gas introduction passage 45e and the
gas guide pipe Ilk to a region near the sealed portion 44 of the
cylindrical MEA 7.
[0085] The gas transfer passage 45 is preferably an elastically
deformable tube passage composed of, for example, a resin. An end
portion of the tube passage is engaged around the outer
circumference of the introduction part 31a and fastened with a
fastener 47. As a result, a connection that is highly airtight can
be obtained. As with the gas transfer passage 45, the gas exhaust
passage 55 is a tube passage; this tube passage is engaged around
the outer circumference of the gas discharge part 31c and fastened
with a fastener 57.
[0086] In an inner region with respect to the engagement portion
45d in the axial direction, an annular exhaust space 46 is formed
that is in communication with the inner space of the cylindrical
MEA 7 and surrounds the gas guide pipe 11k. In a side portion of
the exhaust space 46, the gas discharge part 31c is provided. Gas
exhaust from decomposition in the cylindrical MEA 7 is discharged
through the gas discharge part 31c and the gas exhaust passage
55.
[0087] By employing the pipe joint, introduction and discharge of
gaseous fluids can be achieved at a single end of the cylindrical
MEA 7 without causing mixing of a gas to be decomposed and
decomposed gases.
[0088] In the body portion 31 of the pipe joint 30, a conductive
penetration part 37c that penetrates the body portion 31 in an
airtight manner is provided. To ensure the airtightness, for
example, a sealing resin 38 is applied. The conductive penetration
part 37c is preferably a cylindrical rod threaded for screwing a
nut 39 for the purpose of ensuring electrical connection with the
external wire 11e. To the intra-pipe end of the conductive
penetration part 37c, a conductive lead 37b is connected. Another
end 37a of the conductive lead 37b is bonded to an outer
circumferential portion of the gas guide pipe 11k with an annular
clamp 34.
[0089] By employing the above-described configuration, the
connection resistance between the gas guide pipe 11k and the
external wire 11e can be decreased.
[0090] By winding an external wire 12e around the outer
circumference of an end portion of the Ni mesh sheet 12a of the
cathode collector 12, connection to the outside can be established.
Since the second electrode layer (cathode) 5 is positioned on the
outer-surface side of the cylindrical MEA 7, the establishment of
the connection is less difficult than that from the anode collector
11 to the outside.
[0091] As illustrated in FIG. 4, both of the connection between the
anode collector 11 and the external wire 11e and the connection
between the pipe joint 30, the gas transfer passage 45, and the gas
exhaust passage 55 can be achieved in a small space. In addition,
these two connections are disposed at positions that are separated
from the main stream of thermal flow from the heater. Accordingly,
use of a heat-resistant resin or a corrosion-resistant resin such
as a fluorocarbon resin can ensure durability for repeated use for
a long period of time.
[0092] In the present embodiment, the silver-paste-coated layer 11g
is disposed as a porous conductive layer on an inner
circumferential portion of the first electrode layer (anode) 2; and
the Ni mesh sheet 11a is connected to the first electrode layer 2
with the silver-paste-coated layer 11g therebetween.
[0093] Silver pastes that provide a porous structure by being
applied and dried (fired) are commercially available. For example,
DD-1240 manufactured by Kyoto Elex Co., Ltd. may be used. By
forming the silver-paste-coated layer 11g so as to have a porous
structure, a large number of ammonia molecules (NH.sub.3) enter
pores in the porous structure and come into contact with a catalyst
in the first electrode layer (anode) 2, increasing the probability
of the occurrence of the anode reaction.
[0094] To increase the gas decomposition reaction efficiency, the
porosity of the silver-paste-coated layer 11g is preferably made
20% to 80%. When the porosity is less than 20%, it becomes
difficult to introduce the gas into the conductive-paste-coated
layer and the efficiency is not increased. On the other hand, when
the porosity is more than 80%, it is difficult to ensure
sufficiently high conductivity and the coated layer does not have
sufficiently high strength. More preferably, the porosity is made
40% to 60%.
[0095] The silver-paste-coated layer 11g may have a thickness of 5
to 300 .mu.m. When the thickness is less than 5 .mu.m, uniform
contact with the silver-paste-coated layer 11g is not achieved over
the entire region of the Ni mesh sheet 11a and it is difficult to
ensure sufficiently high conductivity. When the thickness is more
than 300 .mu.m, a paste-coated layer having sufficiently high
porosity is difficult to form. In order to ensure conductivity and
porosity, the thickness of the silver-paste-coated layer 11g is
more preferably 5 to 100 .mu.m.
[0096] A process for forming the silver-paste-coated layer 11g is
not particularly limited. The silver-paste-coated layer 11g can be
formed by, for example, a dipping process in which the cylindrical
MEA 7 is dipped in a dipping layer filled with a silver paste or a
process in which a coating nozzle is inserted to spray a silver
paste on the inner surface of the cylindrical MEA 7.
[0097] A process for forming the silver-paste-coated layer 11g so
as to be porous is also not particularly limited. In order to
achieve the above-described predetermined porosity, a silver paste
containing a predetermined amount of a binder that evaporates at a
predetermined temperature may be employed. In order to suppress
shrinkage of the conductive-paste-coated layer due to evaporation
of a binder, a binder that sublimes is preferably added. For
example, a silver paste containing a naphthalene-based binder is
preferably employed.
[0098] Although a region in which the silver-paste-coated layer 11g
is formed is also not particularly limited, the silver-paste-coated
layer 11g is preferably formed over the entire surface of the first
electrode layer (anode) 2. By forming the silver-paste-coated layer
11g over the entire surface of the first electrode layer (anode) 2,
even when a portion of the Ni mesh sheet is separated from the
silver-paste-coated layer, the current-collecting capability for
the first electrode layer (anode) 2 is not degraded.
[0099] A powder material for forming the solid electrolyte layer 1
may be a solid oxide, molten carbonate, phosphoric acid, a solid
polymer, or the like. The solid oxide is preferred because it can
be used in a small size and easily handled. Preferred examples of
the solid oxide include oxygen-ion-conductive oxides such as
scandium stabilized zirconia (SSZ), yttrium stabilized zirconia
(YSZ), samarium stabilized ceria (SDC), lanthanum gallate (LSGM),
and gadolia-stabilized ceria (GDC). Alternatively,
proton-conductive barium zirconate may be used. The powder
materials may be fired by, for example, being held in the air
atmosphere at 1000.degree. C. to 1600.degree. C. for 30 to 180
minutes.
[0100] The first electrode layer (anode) 2 may be formed as a fired
body mainly composed of metal chain particles whose surfaces are
oxidized to have oxide layers and an oxygen-ion conductive ceramic.
Examples of the oxygen-ion conductive ceramic include SSZ (scandium
stabilized zirconia), YSZ (yttrium stabilized zirconia), SDC
(samarium stabilized ceria), LSGM (lanthanum gallate), and GDC
(gadolia-stabilized ceria).
[0101] When SSZ is employed, the average particle size thereof is
preferably about 0.5 .mu.m to about 50 .mu.m. The firing step may
be performed by, for example, holding in the air atmosphere at
1000.degree. C. to 1600.degree. C. for 30 to 180 minutes. A SSZ
raw-material powder preferably has an average particle size of
about 0.5 .mu.m to about 50 .mu.m. The mixing ratio (mol ratio) of
the metal chain particles whose surfaces are oxidized to SSZ is in
the range of 0.1 to 10.
[0102] The metal of the metal chain particles is preferably nickel
(Ni) or iron (Fe)-containing Ni. More preferably, the metal
contains titanium (Ti) in a trace amount, about 2 to about 10000
ppm.
[0103] The metal chain particles are preferably produced by a
reduction precipitation process. This reduction precipitation
process for the metal chain particles is described in detail in,
for example, Japanese Unexamined Patent Application Publication No.
2004-332047. The metal chain particles contained in the first
electrode layer (anode) 2 preferably have an average diameter D of
5 nm or more and 500 nm or less, and an average length L of 0.5
.mu.m or more and 1000 .mu.m or less. The ratio of the average
length L to the average diameter D is preferably 3 or more. Note
that the metal chain particles may have dimensions that do not
satisfy these ranges.
[0104] The second electrode layer (cathode) 5 is formed of a fired
body mainly composed of an oxygen-ion-conductive ceramic. In this
case, examples of the oxygen-ion-conductive ceramic include
lanthanum strontium manganite (LSM), lanthanum strontium cobaltite
(LSC), and samarium strontium cobaltite (SSC). Such powder
materials may also be fired under the above-described
conditions.
[0105] FIG. 5 illustrates a second embodiment of the present
invention. In this embodiment, an end portion of the cylindrical
MEA 7 is sealed with a sealing member 50 to form the sealed portion
44. The configurations other than the sealed portion 44 are the
same as in the first embodiment and hence are not described.
[0106] The sealing member 50 is formed of a heat-resistant resin
such as a Teflon (registered trademark of E. I. du Pont de Nemours
and Company) resin. The sealing member 50 includes a side wall
portion 50a that can engage with an outer circumferential portion
of the solid electrolyte layer 1 and a bottom portion 50b that
seals an end of the side wall portion 50a.
[0107] The side wall portion 50a is connected such that an O-ring
53 contained on the inner-surface side of the side wall portion 50a
butts against the outer surface of the solid electrolyte layer 1
composed of a ceramic, which is a fired body. The side wall portion
50a is formed so as to have a tapered portion in the outer
circumference. The tapered portion is threaded and, to this thread,
a circular nut 52 is screwed. By screwing the circular nut 52 in
the direction in which the outer diameter increases, a side wall
portion 50c is tightened in its outer surface. Thus, the
airtightness can be ensured with the O-ring 53.
[0108] By employing the above-described configuration, a gas
decomposition component according to the present invention can be
easily provided with a cylindrical MEA having two open ends.
[0109] In the above-described embodiments, the present invention is
applied to a gas decomposition component intended for gas
detoxification. The present invention is also applicable to gas
decomposition components whose main purpose is not gas
detoxification and to cylindrical MEAs of electrochemical reaction
apparatuses. For example, the present invention is also applicable
to cylindrical MEAs of fuel cells or power generation
apparatuses.
[0110] Embodiments of the present invention have been described
above. However, embodiments of the present invention disclosed
above are given by way of illustration, and the scope of the
present invention is not limited to these embodiments. The scope of
the present invention is indicated by Claims and embraces all the
modifications within the meaning and range of equivalency of the
Claims.
INDUSTRIAL APPLICABILITY
[0111] A gas decomposition component that operates at a low running
cost and has a small size and high performance can be provided at a
low cost.
REFERENCE SIGNS LIST
[0112] 1 solid electrolyte layer [0113] 2 first electrode layer
(anode) [0114] 5 second electrode layer (cathode) [0115] 7
cylindrical MEA [0116] 44 sealed portion [0117] 11k gas guide pipe
[0118] 43 cylindrical channel
* * * * *